Dental ceramic firing ovens

ABSTRACT

A dental firing oven of a compound type having two firing chambers in an upper housing and respectively provided for (1) firing porcelain dental products into fused condition and for (2) effecting preliminary burning of expendable materials, such as binders for the porcelain particles. The firing chambers open downwardly to receive products supported on product carriers movable toward and from a lower housing in which control and actuating mechanism is mounted for actuating said product carriers.

United States Patent Schaun [54] DENTAL CERAMIC FIRING OVENS [72] Inventor:

Wolfgang Eugen Schaun, Buchschlag, Germany Dentsply International Inc., York, Pa. Dec. 22, 1970 Assignee:'

Filed:

Appl. No.:

U.S. Cl ..2l9/390, 13/22, 219/394, 219/406, 219/477, 219/478, 219/537 Int. Cl ..F27b 5/14 Field of Search ..219/390, 394, 406, 477-478, 219/537; 13/22, 25, 31

[56] References Cited UNITED STATES PATENTS 838,647 12/1906 Roach ..219/390 1,926,344 9/1933 Meyer...; ..219/394 X 1,534,592 4/1925 Houck ..219/390 [151 3,655,941 [451 Apr.ll, 1972 1,750,804 3/1930 Hollenback ..219/390 3,128,326 4/1964 Hintenberger ..l3/3l FOREIGN PATENTS OR APPLICATIONS 895,821 5/1962 Great Britain ..219/390 Primary Examiner-Volodymyr Y. Mayewsky Attorney-C. Hercus Just 57 ABSTRACT A dental firing oven of a compound type having two firing chambers in an upper housing and respectively provided for (l) firing porcelain dental products into fused condition and for (2) effecting preliminary burning of expendable materials, such as binders for the porcelain particles. The firing chambers open downwardly to receive products supported on product carriers movable toward and from a lower housing in which control and actuating mechanism is mounted for actuating said product carriers.

3 Claims, 2 Drawing Figures PATENTEDAPR 11 m2 3,655,941 sum 2 UF 2 M MM Wen/w? WOLFGANG fME/v 56/04 (IN DENTAL CERAMIC FIRING OVENS This invention-relates to a dental ceramic firing oven, comprising a two-part housing, the upper housing portion being spaced above the lower housing portion provided with indicating and controlling elements, elements for accepting a product to be fired being constructed to be movable into said upper housing portion from the bottom.

Dental ceramic firing ovens of the specified type are conventional as electrically heatable dental ceramic firing ovens having a vertical firing chamber, in which a vertical movement of the product to be fired is effected by means of a vertically shiftable product carrier, the firing chamber being open at the bottom in order to introduce the product to be fired by means of the product carrier from the bottom, said product carrier being capable of being loaded in the fully extended condition.

Furthermore, a dental ceramic firing oven has already been proposed in which a vertical firing chamber tightly closed at the top is charged from the bottom upwardly by means of movable product carrier means comprising a closure block closing the firing chamber downwardly and a closure plate closing the firing chamber from the outside. Small columns between the closure block and the closure plate leave free a void which is dimensioned and formed in such a way that the product to be treated can be accommodated therein for a preheating operation.

The ovens constructed in this way do have various disadvantages, although the actual firing operation of dental ceramic objects to be fired can be effected broadly satisfactorily, namely in particular regarding an economical and reliable conductability of the various measures necessary. for performing dental ceramic operations.

The dental ceramic operations necessary for the production of dental protheses of dental ceramic masses comprise the steps of predrying and preheating the fire product, the burning of the organic dyes and possible binders as well as the actual firing process which is in part effected in vacuum and in part under atmospheric air pressure. In addition thereto dental ceramic procedures of a specialized nature such as the socalled fire-application ceramics in which dental ceramic masses are fused onto metal backings of noble metal or nonnoble metal additionally require not actually firing-technological measures such as the annealing of the metal backing prior to the fire application of the masses or heat-treating of the completed objects.

A part of the specified operations (predrying, preheating the product to be fired, burning the organic dyes, annealing the metal backing, heat-treatingthe completed objects etc.) now must be conducted at temperatures which prevailingly are below the actual firing temperatures which are required for the firing of the masses or for accomplishing the desired degree of gloss, and in addition thereto dental ceramic fire objects such as jacket crowns or crowns and bridges according to the so-called fire-application ceramics must be prepared of a plurality of consecutive mass layers corresponding to the structure of natural teeth and consequently the masses require a plurality of firing processes or must be fired several times.

In addition thereto the above specified operations (pre-drying and preheating the product to be fired) are to be given credit of just as high a process-technological and materialtechnological importance in the scope of the production of dental ceramic products as the actual firing process, in particular because these operations like the firing process must be performed in maintaining specific temperatures and periods of time.

This requires that in the type of dental ceramic firing ovens conventional up to now which has a vertical product feeding arrangement the product positioning as well as the positioning of the product carrier must be changed prior to the actual firing process several times and at least in part manually.

Moreover the described measures are conducted over an extended period of time with respectively entirely or partly opened firing chamber, and this has an adverse effect in the firing oven mentioned hereinbefore on the performance capacity and the life of the heating coil.

This shows that an economical and rapid course of operations is not insured with dental ceramic firing ovens of the conventional type having only one firing chamber or only one product carrier which must be utilized also for all secondary measures of the type described hereinbefore.

An object of the invention is to provide a firing oven which on the one hand permits a reliable and also rapid working for the user and on the other hand insures a process technology even better adapted to the dental ceramic material.

According to the invention, a firing oven of the specified type is characterized in that in the upper housing portion two firing chambers independent of one another are provided juxtaposed and two product carriers associated to said firing chambers are provided in said lower housing portion, said product carriers being constructed movable elevator-like into said firing chambers.

The mentioned disadvantages of one-chamber ovens can be overcome with this construction of a twin-lift firing oven, by for instance using the right-hand firing chamber or the righthand product carrier preferred for drying, preheating etc. the products to be fired, while the actual firing operation is then conducted in the left-hand firing chamber or by means of the left-hand product carrier.

With the foregoing object in view, together with such additional objects and advantages as may subsequently appear, the invention resides in the parts, and in the construction, combination, and arrangements of parts disclosed, by way of example, in the following specification of certain modes of execution of the invention; reference being had to the accompanying drawings which form a part of said specification and in which drawings:

FIG. 1 is a side elevation of the oven and FIG. 2 is a part-sectional view of the oven disclosed in H6.

In FIG. 1 1 denominates the upper housing portion, 2 and 3 denominate the firing chambers shown in phantom which are open at the bottom and are located in the housing portion 1, to which firing chambers two product carriers 5 and 6 are associated of the lifting means of which which are positioned in the lower housing portion 4 merely the upper ends of the two reciprocating rods 7, 8 are shown.

The firing chambers 2 and 3 are of similar construction internally and the sectional view of chamber 2 shown in FIG. 2 is considered to illustrate the internal construction of Chamber 3. In such interior construction of the chambers 2 and 3, convention firebrick 2a used in dental firing furnaces is mounted to provide the firing space 2b which extends upwardly into the heater unit 20 which is defined by ceramic insulating material and provided with grooves in which an electric resistance heating element 2d is mounted, all parts of said heater unit 20 being formed from the type of material conventionally used in dental firing furnaces.

The upper housing portion 1 is spaced by columns 9, 10 from the lower housing portion 4 in a manner known per se, and the front face of which lower housing portion various controlling, adjusting and actuating elements are arranged necessary for the operation of the oven.

In FIG. 2 l1 denominates a connector for a vacuum pump (not illustrated) from which a conduit extends to the vacuum distributor 12. A conduit 13 extends from the distributor 12 to which a valve 14 is associated to the lower end 15 of the hollow lift rod 8, and in this region a limit switch 16 can also be provided. The rods 7, 8 are mounted in gear casings 17 in which pinions or rotatably mounted screws transmit the reciprocating movements depending on the configuration of the rods 7, 8 as racks or threaded spindles. Closure plates 18, 19 are arranged underneath the product carriers 5, 6, which tightly close the firing chambers 2, 3 when rods 7, 8 are extended upwardly.

The motors for the operation of the gearings located in the housings or casings 17 for the movement of the reciprocating rods 7, 8 are not illustrated.

The two product carriers 5, 6 are advantageously provided with lifting means movable independent of one another in the lower housing portion 4, at least one of the lifting means likewise in view of the various treatment steps advantageously being constructed to be intermittently drivable for instance in that the predrying and preheating operations of the products to be fired as well as the burning of organic proportions in the dental ceramic masses is effected automatically without any I manual change in the product to be fired regarding its positioning, but merely by means of an intermittent introduction of the product carrier into the firing chamber 3. This intermittent moving-in is caused for instance by means of a timer or a program actuator 20 which is in an electrical connection to the motor for the gearing in the right-hand casing 17.

Notwithstanding the illustrated uses of the invention and the manners by which such uses may be achieved, it is appreciated that changes and modifications will suggest themselves to others skilled in the art both for usessimilar to those illustrated as well asfor other uses. The invention, therefore, is not to be deemed to be limited to the exact modes of execution above disclosed by way "of example, and it will be understood that the invention embraces all such changes and modifications in the parts, and in the construction, combination and arrangement of parts as whall come within the purview of the appended claims.

What is claimed is:

l. A dental ceramic firing oven comprising a lower housing, an upper housing, and means supporting the same in spaced relation to and above said lower housing, a firing oven chamber for ceramic dental porcelain materials in said upper housing having an inlet opening in the lower end of said upper housing and electrical heating means therefor, a product carrier mounted for vertical movement relative to and supported by said lower housing, and mechanical means within said lower housing operable to move said product carrier toward and from said firing oven chamber inlet to support ceramic dental items for firing within said firing oven, in combination with a second oven chamber within said upper housing laterally spaced from said firing oven chamber and provided with an inlet opening in the lower end of said upper housing, electrical heating means for said second oven chamber to heat the same to a lower temperature than said firing oven chamber to pre-dry and pre-heat and burn out organic materials in dental ceramic products under conditions of controlled temperatures and time, a second product carrier mounted for vertical movement relative to and supported by said lower housing, additional mechanical means within said lower housing operable to move said second product carrier toward and from the inlet of said second oven chamber, and a timer operable to control the length of time said product carrier supports a dental product within said second oven chamber and then lower the same from said chamber.

2. The oven according to claim 1 in which said mechanical means to move said product lifting means toward and from the inlets of said oven chambers are adapted to be operated independently of each other.

3. The oven according to claim 1 in which said additional mechanical means to move said product lifting means of said second oven chamber is adapted to be operated intermittently of the means to move said product lifting means of said first mentioned oven chamber. 

1. A dental ceramic firing oven comprising a lower housing, an upper housing, and means supporting the same in spaced relation to and above said lower housing, a firing oven chamber for ceramic dental porcelain materials in said upper housing having an inlet opening in the lower end of said upper housing and electrical heating means therefor, a product carrier mounted for vertical movement relative to and supported by said lower housing, and mechanical means within said lower housing operable to move said product carrier toward and from said firing oven chamber inlet to support ceramic dental items for firing within said firing oven, in combination with a second oven chamber within said upper housing laterally spaced from said firing oven chamber and provided with an inlet opening in the lower end of said upper housing, electrical heating means for said second oven chamber to heat the same to a lower temperature than said firing oven chamber to pre-dry and pre-heat and burn out organic materials in dental ceramic products under conditions of controlled temperatures and time, a second product carRier mounted for vertical movement relative to and supported by said lower housing, additional mechanical means within said lower housing operable to move said second product carrier toward and from the inlet of said second oven chamber, and a timer operable to control the length of time said product carrier supports a dental product within said second oven chamber and then lower the same from said chamber.
 2. The oven according to claim 1 in which said mechanical means to move said product lifting means toward and from the inlets of said oven chambers are adapted to be operated independently of each other.
 3. The oven according to claim 1 in which said additional mechanical means to move said product lifting means of said second oven chamber is adapted to be operated intermittently of the means to move said product lifting means of said first mentioned oven chamber. 